[3] The imperial shag has a total length of 70–79 cm (28–31 in) and weighs 1.8–3.5 kg (4.0–7.7 lb), with males usually larger than females.

It possesses a distinctive ring of blue skin around its eyes, an orange-yellow nasal knob, pinkish legs and feet, and an erectile black crest.

[7] During the non-breeding season, adults lack the crest, have a duller facial area, and less or no white to the back and wings.

The colonies are usually relatively small, but some consist of hundreds of pairs and are often shared with other seabirds such as rock shags, southern rockhopper penguins and black-browed albatrosses.

[11] The diet of this species consists of small benthic fish, crustaceans, polychaetes, gastropods and octopuses.